Communication terminal having function for displaying originator identification data

ABSTRACT

A communication terminal connected to an analog telephone network and has a function for transmitting an incoming call signal with originator identification data inserted. Notification of an incoming call is stopped during a time period from the detection of a first ringing signal of the incoming call signal to the detection of the originator identification data. A user is notified of the presence of the incoming call is notified after the originator identification data is detected and notified to the user.

This is a continuation of application Ser. No. 08/834,870, filed Apr.10, 1997, now U.S. Pat. No. 5,799,074 which is a continuation ofapplication Ser. No. 08/368,600, filed Jan. 4, 1995, now abandoned, andclaims the benefit of Japanese application no. 6-000512, filed Jan. 7,1994, all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a communication terminal connected to a publicnetwork such as a telephone, a key telephone system, or a private branchexchange, and more particularly to a communication terminal having afunction for receiving and displaying originator identification data tobe transmitted from the public network to a destination.

2. Description of the Related Art

Analog telephone networks include a network having a function fornotifying a destination subscriber of originator identification data,such as a telephone network for providing a service called "CLASS".

In an analog telephone network with such a function, originatoridentification data is notified to a destination in the followingmanner:

In the case of transmitting an incoming call signal by such an analogtelephone network as has the "CLASS" service, a ringing signal of apredetermined frequency which continues two seconds is repeatedlytransmitted at intervals of four seconds. Notification data fortransmitting originator identification data is transmitted within aninterval between the first and second ringing signals of the incomingcall signal. A pose period of 0.5 seconds is inserted between thetermination point of the first ringing signal and the start point of thenotification data. The transmission period of the communication data is575 ms. The format of the notification data is determined such that asynchronization signal of a "01"-repeated pattern, a mark signal, amessage-type word, a data work count, a data section and a check sum arearranged in this order. The originator identification data contains"date/hour" and "originator number".

In the case of using a key telephone system as a communication terminal,the key telephone system detects, with the use of its key telephonecontrol unit, notification data after detecting the first ringingsignal. When the control unit has detected originator identificationdata from the notification data, it transmits the originatoridentification data to a destination key telephone, which in turndisplays the data on its display unit. The user of the destination keytelephone can recognize the originator of the call by seeing theoriginator identification data on the display.

The above-described conventional key telephone system, however, has thefollowing drawback:

Suppose that the key telephone control unit has detected the firstringing signal transmitted from an analog network. Upon detecting theringing signal, the key telephone control unit starts the transmissionof a ringing signal to a destination key telephone, thereby causing thekey telephone to ring so as to start notification of the incoming call.Subsequently, when the key telephone control unit has detected theoriginator identification data in the interval between the first andsecond ringing signals, it transmits the identification data to thedestination key telephone, which in turn displays the data.

In other words, the key telephone rings before it displays theoriginator identification data.

Therefore, if the user performs a prompt off-hook operation immediatelyafter he has heard the ringing, it is possible that he receives nooriginator identification data, since the transmission of the incomingcall signal is ceased when a call response has been performed. Arelatively large number of users perform a prompt off-hook operation ina conditioned reflex manner when they have heard a telephone ringing.Therefore, the above problem occurs in unexpectedly many cases.

SUMMARY OF THE INVENTION

It is a first object of the invention to provide a communicationterminal capable of reliably notifying the user of originatoridentification data.

It is a second object of the invention to provide a communicationterminal capable of reliably notifying the user of originatoridentification data and also capable of promptly notifying the user ofan incoming call.

It is a third object of the invention to provide a communicationterminal capable of preventing the user's off-hook operation during atime period from the detection of the first ringing signal to thedetection of originator identification data.

It is a fourth object of the invention to provide a communicationterminal capable of allowing the user to confirm originatoridentification data even after the user responds to a call.

It is a fifth object of the invention to provide a communicationterminal capable of reliably detecting originator identification dataand notifying the user of it even when the user has responded to anincoming call before the notification of originator identification data.

It is a sixth object of the invention to provide a key telephone systemcapable of reliably notifying the user of originator identificationdata.

It is a seventh object of the invention to provide a key telephonesystem capable of reliably detecting originator identification data andnotifying the user of it even when the user has responded to an incomingcall before the notification of originator identification data.

To attain the first object, there is provided a communication terminalconnected via a subscriber line to a network having a function fortransmitting a plurality of ringing signals to the communicationterminal at regular intervals with an originator identification signalinserted in an interval between a k-th (k: a predetermined integer)ringing signal and a (k+1)-th ringing signal, comprising: ringing signaldetection means for detecting the ringing signals transmitted from thenetwork; originator detection means for detecting the originatoridentification signal transmitted from the network; and control means.The control means notifies the user of the communication terminal oforiginator identification data corresponding to the originatoridentification signal detected by the originator detection means, andstarts to notify the user of an incoming call in accordance with theringing signals detected by the ringing signal detection means after thenotification of the originator identification data is started.

Alternatively, the control means notifies the user of the communicationterminal of the originator identification data corresponding to theoriginator identification signal detected by the originator detectionmeans, and prohibits the notification of the incoming call to the userof the communication terminal during a time period from the detection ofa first ringing signal by the ringing signal detection means to thenotification of the originator identification data to the user of thecommunication terminal.

In the invention constructed as above, the notification of the incomingcall is started after the start of the notification of the originatoridentification data. This means that the user is already notified of theoriginator identification data when he or she has noticed the occurrenceof the incoming call from the notification thereof, and therefore he canreliably know the identification data.

To attain the second object, the communication terminal is constructedsuch that the notification of the originator identification data andthat of the incoming call are performed at the same time. This structureenables the occurrence of the incoming call to be notified to the userafter the originator identification data is reliably notified to him.

Further, the following structures i) and ii) may be employed to performthe notification of the originator identification data and that of theincoming call at the same time:

i) A first structure which employs means for generating a pseudo ringingsignal similar to the ringing signal detected by the ringing signaldetection means. In this structure, the notification of the originatoridentification data corresponding to the originator identificationsignal is started when the signal has been detected, and the pseudoringing signal is generated to notify the incoming call within a timeperiod from the start of notification of the originator identificationdata to the detection of the (k+1)-th ringing signal. This structureenables notification of the incoming call with the use of the pseudoringing signal before the detection of the (k+1)-th ringing signal,which means that the occurrence of the incoming call can be notified tothe user promptly.

ii) A second structure which employs a memory for storing the originatoridentification data corresponding to the detected originatoridentification signal. In this structure, the detected originatoridentification data is read from the memory and notified in synchronismwith the notification of the incoming call performed upon detection ofthe (k+1)-th ringing signal. Although in this structure, the start ofnotification of the incoming call and the originator identification datais retarded as compared with the first structure, the pseudo ringingsignal is not necessary.

To attain the third object, the communication terminal has the followingstructures i) and ii):

i) The user is notified of that the originator identification signal isbeing received, during a time period from the detection of the firstringing signal to the detection of the originator identification signal.

ii) The user is notified of that an operation for sending a call isprohibited, during a time period from the detection of the first ringingsignal to the detection of the originator identification signal.

By virtue of the above structures, the user can be indirectly notifiedof that the incoming call is being received, which reduces the number ofoccasions where the user performs an off-hook operation for generatingan outgoing call signal without being aware of the occurrence of theincoming call.

To attain the fourth object, the communication terminal of the inventioncontinues the notification of the originator identification data for apredetermined time period even after the user's operation for respondingto the incoming call is detected. Therefore, the user can confirm theoriginator identification data even during talking.

To attain the fifth object, the communication terminal of the inventionis adapted to invalidate a response of the user to the incoming callduring a time period from the start of notification of the incoming tothe notification of the originator identification data. Accordingly,even if the user performs an operation for responding to the incomingcall before the notification of the originator identification data, therequest for responding to the incoming call is not received until theoriginator identification is detected and notified to the user. As aresult, the transmission of the incoming call signal from the analognetwork is prevented from being stopped before the transmission of theoriginator identification data, and therefore the originatoridentification data from the analog network can be reliably detected andnotified.

Moreover, it may be constructed such that the user is notified that anoperation for responding to the incoming call is prohibited while theresponse thereto is invalidated. This structure enables the user not toperform a response to the incoming call during the response invalidatedperiod. Further, even when the user has performed such an operationirrespective of the prohibition, the operation is invalidated and theoriginator identification data can reliably be notified to the user.

To attain the sixth object, there is provided a key telephone systemwhich employs control means for detecting the originator identificationsignal supplied from the analog network, and notifying the user oforiginator identification data corresponding to the originatoridentification signal. Further, the control means notifies the user ofan incoming call after the display of notification of the originatoridentification data is started. Since the notification of the originatoridentification data is started before the notification of the incomingcall is started, the user is notified of the originator identificationdata before he recognizes the occurrence of the incoming call from itsnotification. Thus, the user can reliably obtain the originatoridentification data.

The above-described control operation may be performed by the keytelephone control unit only, or by each key telephone, or by both thekey telephone control unit and each key telephone.

To attain the seventh object, there is provided a key telephone systemin which a response of the user to the incoming call is invalidatedduring a time period from the start of notification of the incoming callto the start of notification of the originator identification data.Therefore, even if the user performs an operation for responding to theincoming call before the notification of the originator identificationdata, the request for responding to the incoming call is not receiveduntil the originator identification data is detected and notified to theuser. Accordingly, the transmission of the incoming call signal from theanalog network is prevented from being stopped before the transmissionof the originator identification data, and therefore the originatoridentification data from the analog network can be reliably detected andnotified.

The above-described structures are applicable not only to a keytelephone system but also to a private branch exchange, a telephoneapparatus, or an adaptor apparatus interposed between an analog networkand a communication terminal.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention and, together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a schematic view, showing a communication system according toa first embodiment of the invention;

FIG. 2 is a block diagram, showing a key telephone system according tothe first embodiment of the invention;

FIG. 3 is a block diagram, showing a subscriber-line interface unitincorporated in the key telephone system shown in FIG. 2;

FIG. 4 is a block diagram, showing an extension interface unitincorporated in the key telephone system shown in FIG. 2;

FIG. 5 shows an originator number detection unit incorporated in the keytelephone system shown in FIG. 2;

FIG. 6 is a view, showing a data sequence useful in explaining theoperation of the key telephone system of FIG. 2;

FIG. 7 is a view, showing a format of an incoming call signal andnotification data;

FIG. 8 is a block diagram, showing an electronic private branch exchangeaccording to a second embodiment of the invention;

FIG. 9 is a block diagram, showing a telephone device according to athird embodiment of the invention; and

FIG. 10 is a block diagram, showing an adaptor device according to afourth embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

In a first embodiment, a key telephone system is connected to an analogtelephone network with an originator notification function, and isprovided with a notification control function according to theinvention. The notification control function causes an incoming call tobe notified after the notification of originator identification data.

Referring to FIG. 1, an analog telephone network NW is connected, via asingle or a plurality of subscriber lines SL, to a key telephone system,a private branch exchange system and telephones, which serve assubscriber communication terminals. The key telephone system consists ofa key telephone control unit KCU connected to the subscriber lines SL,and a plurality of key telephones EKT connected to the control unit KCUvia key telephone lines KL. The private branch exchange system consistsof a private branch exchange PBX connected to the subscriber lines SL,and a plurality of key telephones TEL connected to the exchange PBX viaextension lines IL.

The analog telephone network NW has a service function for supplying adestination subscriber communication terminal with a notice oforiginator identification data. When a request for a call to asubscriber communication terminal connected to an analog telephonenetwork NW has transmitted to the network, the above service function isexecuted to mix a signal indicative of the originator identificationdata into an incoming call signal to be transmitted to the terminal,thereby supplying the subscriber communication terminal with a notice oforiginator identification data. The request for a call can be senteither from a subscriber communication terminal connected to an analogtelephone network NW to which a destination terminal belongs, or from asubscriber communication terminal connected to another analog telephonenetwork (in this case, via a relay line). When a request for call hasbeen sent from a subscriber communication terminal connected to ananalog telephone network to which a destination subscriber terminalbelongs, identification data for identifying an originator is created bythe analog telephone network. On the other hand, when a request for acall has been sent from a subscriber communication terminal connected toanother analog telephone network, the originator identification data istransmitted from the another analog telephone network, together with therequest for the call.

FIG. 7 shows an example of a format of an incoming call signal andnotification data to be transmitted to a subscriber communicationterminal. The incoming call signal consists of a ringing signal with apredetermined frequency which continues two seconds and is repeatedlytransmitted at intervals of four seconds. The notification data istransmitted in an interval between the first and second ringing signalsof the incoming call signal. A pose period of 0.5 seconds is insertedbetween the termination point of the first ringing signal and the startpoint of the notification data. The transmission period of thenotification data is 575 ms.

The notification data contains a synchronization signal of a"01"-repeated pattern, a mark, a message-type word, a data count word, adata section and a check sum. Each of the message type word, the datacount word, and the check sum is 8-bit data. The length of the dataportion is set to a maximum of 144 bits. The originator identificationdata, which includes "date and hour" and "originator number", isinserted in the data portion. The "date and hour" indicates the date andhour of an incoming call from an originator, while the "originatornumber" indicates a subscriber number imparted to the originator.

The key telephone system having a notification control functionaccording to the invention is constructed as follows:

FIG. 2 is a block diagram, showing the circuit structure of the system.As is shown in FIG. 2, the key telephone system comprises m keytelephones 2 (2-1-2-m) connected to a key telephone control unit 1.

The key telephone control unit 1 has a time switch 10, a timinggenerating circuit 11, n subscriber-line interface units 12 (12-1-12-n),m extension interface units 13 (13-1-13-n), n originator numberdetection units 14 (14-1-14-n), a sub control unit 15, a memory 16 and amain control unit 17. The subscriber-line interface units 12, theextension interface units 13 and the originator number detection units14 are connected to the sub control unit 15 via a data highway 18. Thetime switch 10, the sub control unit 15 and the memory 16 are connectedto the main control unit 17 via a bus 19.

The time switch 10 is connected to the subscriber-line interface units12 and the extension interface units 13 via a PCM highway 20. The timeswitch 10 exchanges time slots on the PCM highway 20 on the basis of thecontrol of the main control unit 17 and various timing signals generatedby the timing generating circuit 11. The connection between thesubscriber-line interface units 12 and the extension interface units 13or between the extension interface units 13 is changed by exchanging thetime slots.

The subscriber-line interface units 12 (12-1-12-n) are connected tosubscriber lines 3 (3-1-3-n), respectively. As is shown in FIG. 3, eachsubscriber-line interface unit 12 has an incoming call detection circuit120, a rectification circuit 121 consisting of a diode bridge, a DCcurrent control circuit 122, a Codec (coder/decoder) 123, and asubscriber-line interface control unit 124. The Codec 123 performs PCMencoding/decoding of a voice signal. The subscriber-line interfacecontrol unit 124 controls the subscriber-line interface unit (controls,for example, detection of an incoming call, seizure of a subscriberline, transmission using a dial, etc.) under the control of the maincontrol unit 17. The subscriber-line interface unit 12 performs asubscriber-line interface operation for the analog telephone network NW.The subscriber-line interface operation includes conversion of an analogvoice signal transmitted via each subscriber line 3, to a PCM signal,conversion of the PCM signal supplied via the time switch 10, to ananalog voice signal, monitoring of the state of each subscriber line 3,transmission of various signals to the analog telephone network NWconnected to the interface unit 12 via the subscriber lines 3, etc.Further, the subscriber-line interface unit 12 sends and receivescontrol data relating to the subscriber-line interface operation, to andfrom the main control unit 17 via the sub control unit 15.

The extension interface units 13 (13-1-13-m) are connected to the keytelephones 2 (2-1-2-m), respectively. As is shown in FIG. 4, eachextension interface unit 13 has an extension interface control unit 130,a memory 131 and a digital transmission unit 132. The extensioninterface control unit 130 transmits control data via the data highway18. The memory 131 serves as an external memory of the control unit 130.The digital transmission unit 132 transmits control data and voice databetween the key telephone 2 and the key telephone control unit 1.Further, the extension interface unit 13 performs an extension interfaceoperation for the key telephones 2. The extension interface operationincludes conversion of an analog voice signal from the key telephones 2,to a PCM signal, conversion of a PCM signal supplied to the extensioninterface unit via the time switch 11, to an analog voice signal,monitoring of the key telephones 2, transmission of various signals tothe key telephones 2, etc. Moreover, each extension interface unit 13receives and sends control data relating to the extension interfaceoperation, to and from the main control unit 17 via the sub control unit15.

The originator number detection units 14 (14-1-14-n) are connected tothe subscriber lines 3 (3-1-3-n), respectively. As is shown in FIG. 5,each originator number detection unit 14 comprises a relay 140, ademodulation circuit 141, a serial/parallel conversion unit 142, a datadetection signal-transmitting unit 144, a relay control unit 145, adetection unit control section 146, and a memory 147.

The relay 140 is used to disconnect the originator number detectionunits 14 from the subscriber lines 3. The demodulation circuit 141receives a modulated signal (notification data signal) from the analogtelephone network NW via the subscriber lines 3, and then demodulatesthe signal to detect the originator identification data. Theserial/parallel conversion unit 142 converts, to a parallel signal, aserial signal supplied from the demodulation circuit 141 and indicativeof the originator identification data. The data detection signal-transmitting unit 144 transmits the originator identification data fromthe modulation circuit 141, to an internal data bus 143. Thenotification data is transmitted to the main control unit 17 via the subcontrol unit 15. The relay control unit 145 controls the relay 140 so asto disconnect the originator number detection unit 14 from thesubscriber line 3 and perform impedance matching at the time of a dialoperation or of talking. The detection unit control section 146 controlsthe originator number detection unit 14. The memory 147 is used as anexternal memory of the detection unit control section 146.

The sub control unit 15 mainly comprises a micro computer, for example,and transmits data between the main control unit 17 and thesubscriber-line interface unit 12, the extension interface unit 13 andthe originator number detection unit 14. The memory 16 is used as anexternal memory of the main control unit 17 for storing various datapieces.

The main control unit 17 mainly comprises, for example, a microcomputer,and has an incoming call control function and a response-inhibitingfunction, as well as general control functions to be employed in the keytelephone control unit 1. Incoming call control means performsprocessing for causing the key telephone 2 to ring after the originatoridentification data is detected from an incoming call signaltransmitted. Response inhibiting means performs processing forinhibiting response to an incoming call by the key telephone 2 for apredetermined period.

The key telephone 2 is constructed as follows:

The key telephone 2 has a speech circuit 21, a handset 22, aninput/output interface circuit 23, dial keys 24, a function key group25, an LED group 26, an LED driving circuit 27, an LCD 28, an LCDdriving circuit 29, a memory 30 and a telephone control unit 31. Thespeech circuit 21, the input/output interface circuit 23, the dial keys24, the function key group 25, the LED driving circuit 27, the LCDdriving circuit 29, and the memory 30 are connected to the telephonecontrol unit 31 via a bus 32.

The speech circuit 21 is connected to the handset 22 and the extensioninterface unit 13 of the key telephone control unit 1. The earpiecespeaker 22b of the handset 22 is driven by a voice signal supplied fromthe extension interface unit 13, a voice signal output from themicrophone 22b of the handset 22 is transmitted to the extensioninterface unit 13.

The input/output interface circuit 23 is connected to the extensioninterface unit 13 for receiving and outputting data to be transmittedbetween the key telephone control unit 1 and the key telephone 2. Thedial keys 24 comprise 12 keys consisting of numeral keys "0"-"9", andsymbol keys "*" and "#". These keys are used by the user to input to thetelephone control unit 31 various data pieces including dial data.

The function key group 25 consists of a plurality of function keys forexecuting a function for designating a subscriber line to catch, etc.The user pushes the function keys to cause the telephone control unit 31to execute the functions.

The LED group 26 consists of a plurality of LEDs corresponding to thefunction keys of the function key group 25. Each of the LEDs indicateswhether or not the function assigned to a corresponding function key isexecuted. The LED driving circuit 27 drives each LED of the LED group 26under the control of the telephone control unit 31. The LCD 28 displaysvarious data for the user. The LCD driving circuit 29 drives the LCD 28under the control of the telephone control unit 31.

The telephone control unit 31 is mainly constituted, for example, by amicrocomputer, and controls each of the key telephones 2. The memory 30stores all data items necessary for the control unit 31 to performvarious processing.

An explanation will be given of how the key telephone system,constructed as above, receives an incoming call, referring to FIGS. 6and 7.

Suppose that a first ringing signal has been supplied from the analogtelephone network NW via the subscriber line 3-1. At this time, thefirst ringing signal is detected by the incoming call detecting circuit120 of the subscriber-line interface unit 12-1 connected to thesubscriber line 3-1. A notice of the detection of the first ringingsignal is given from the subscriber-line interface control unit 124 tothe main control unit 17 via the data highway 18, the sub control unit15 and the bus 19.

Upon receiving the notification of the detection of the first ringingsignal, the main control unit 17 sets a privacy mode for the subscriberline 3-1, and supplies the key telephones 2-1-2-m with LED-lightingdata, thereby continuously lighting the LED of the key corresponding tothe subscriber line 3-1. In other words, in each of the key telephones2-1-2-m, that LED of the LED group 26 which corresponds to thesubscriber line 3-1 is lighted, which indicates that the subscriber line3-1 cannot be used now. At this time, even if that key of the functionkey group 25 which is provided for selecting the subscriber 3-1 ispushed, the main control unit 17 ignores this. Thus, the transmission ofa call from the key telephones 2-1-2-m to the subscriber line 3-1 isprohibited.

Then, suppose that notification data which contains the originatoridentification data has been supplied from the analog telephone networkNW, following to the first ringing signal. The notification data isdemodulated by the demodulation circuit 141 in the originator numberdetection unit 14-1, reproducing the originator identification data. Theoriginator identification data is converted to a parallel signal by theserial/parallel conversion unit 142, and then transmitted to the maincontrol unit 17 via the internal data bus 143, the detection unitcontrol section 146, the data highway 18, the sub control unit 15 andthe bus 19. Upon receiving the originator identification data, the maincontrol unit 17 decodes and stores the date/hour and the originatornumber contained in the identification data, and then waits the supplyof a second ringing signal.

When 4 seconds have elapsed after the transmission of the notificationdata including the originator identification data and the transmissionof the first ringing signal, the analog telephone network NW transmitsthe second ringing signal to the subscriber line 3-1. Then, thesubscriber-line interface unit 12-1 detects the second ringing signal inthe same manner as the first ringing signal, and gives a notice of thedetection of the second ringing signal to the main control unit 17. Uponnotification of the detection of the second ringing signal, the maincontrol unit 17 supplies the key telephones 2-1-2-m with LCD displaydata containing the date/hour and the originator number.

In each of the key telephones 2-1-2-m, the LCD display data is fetchedby the input/output interface circuit 23, and then supplied to the LCDdriving circuit 29 via the bus 32. The LCD driving circuit 29 drives theLCD 28 under the control of the telephone control unit 31. As a result,the LCD 28 displays the date/hour and the originator number.

Subsequently, the main control unit 17 of the key telephone control unit1 supplies the key telephones 2-1-2-m with LED-flickering datasubstantially at the same time as the transmission of the LCD displaydata of the date/hour and the originator number. Further, main controlunit 17 cancels the privacy mode, then generates an incoming call signalin synchronism with the ringing signal, and transmits the signal to thekey telephones 2-1-2-m. As a result, in each of the telephones 2-1-2-m,the LED of a key corresponding to the subscriber line 3-1 is lighted,and the telephone rings. Thus, the user is notified of an incoming callon subscriber line 3-1. At the same time as the start of thenotification of the incoming call, each of the key telephones 2-1-2-mstarts to receive the response to the incoming call by pushing apredetermined key of the function key group 25 for selecting thesubscriber line 3-1.

In this state, suppose that the user of the key telephone 2-1 has pushedthe key corresponding to the subscriber line 3-1 so as to respond to theincoming call. Then, the key input is received by the telephone controlunit 31 of the key telephone 2-1, and then transmitted to the maincontrol unit 17 via the bus 32, the input/output interface circuit 23,the extension interface unit 13-1, the data highway 18 and the bus 19.The main control unit 17, in turn, supplies the subscriber-lineinterface unit 12-1 with an instruction to execute an off-hookoperation, thus responding to the incoming call through the subscriberline 3-1.

As described above, in the key telephone system according to the firstembodiment, there is no flickering of the LED 26 or no telephone ringingfor indicating an incoming call at the key telephone 2-1-2-m, when thefirst ringing signal has been transmitted from the analog telephonenetwork NW. The LED 26 flickers and the telephone rings to indicate theincoming call for the first time when the second ringing signal has beenreceived. By virtue of this structure, the user is kept unaware of theincoming call during the time period from the arrival of the firstringing signal to the arrival of the second ringing signal, and hencedoes not respond thereto. Accordingly, the analog telephone network NWcan reliably transmit the originator identification data without thetransmission of the incoming call signal interrupted. Thus, the keytelephone system can reliably detect the originator identification datafrom the analog telephone network NW, and display the data on the LCD 28of each of the key telephones 2-1-2-m.

Further, in the first embodiment, during the time period from thearrival of the first ringing signal to the arrival of the second ringingsignal, the privacy mode is set in each of the key telephones 2-1-2-m inrespect of that one of the subscriber lines 3 at which an incoming callhas occurred, thereby preventing further key operation for selecting thesubscriber line now being used. Therefore, even if the user performs anoperation for sending a call, this operation is ignored during the timeperiod from the arrival of the first ringing signal to the arrival ofthe second ringing signal. Thus, the analog telephone network NWtransmits the originator identification data without the transmission ofthe incoming call signal interrupted. As a result, the key telephonesystem can reliably detect the originator identification data from theanalog telephone network NW, and display the data on the LCD 28 of eachof the key telephones 2-1-2-m.

Moreover, since in the first embodiment, the LED 26 is lighted while theoriginator identification data is waited after the detection of thefirst ringing signal, this enables the user to easily understand thereason why the operation for sending a call is ignored.

In addition, since in the embodiment, the display of the originatoridentification data on the LCD 28 and the ringing of the telephone areperformed substantially simultaneously when the second ringing signalhas been received, the user does not have to wait until the originatoridentification data is displayed. In other words, when the user hasheard the telephone ringing and looked at the LCD 28, the originatoridentification data has already been displayed thereon or is displayedpromptly.

The above-described embodiment can be modified in various manners. Forexample, although in the embodiment, the display of the originatoridentification data on the LCD 28 and the ringing of the telephone areperformed substantially simultaneously when the second ringing signalhas been received, this processing can cause the following disadvantage.During the time period from the arrival of at least the first ringingsignal to the arrival of the second ringing signal, i.e., during 6seconds, the incoming call is not notified to the user. Therefore, thecall originator may at worst imagine that the person who the originatorwants to contact is absent, and stop the call.

The disadvantage can be avoided by starting the display of theoriginator identification data and the notification of the incoming callupon detection of the originator identification data. In this case, thenotification of the incoming call is performed by generating a pseudocall signal upon detection of the originator identification data, andcausing the key telephone to ring in response to the pseudo call signalgenerated.

Thus, the key telephone can notify the user of the incoming callimmediately after the detection of the originator is identificationdata. More specifically, the user is notified of the incoming call when3 or 4 seconds has elapsed after the detection of the first ringingsignal. Thus, a response to the incoming call can be performedrelatively promptly, minimizing erroneous recognition of the originator.

Further, although in the first embodiment, the LED 26 is lighted whilethe originator identification data is awaited after the detection of thefirst ringing signal, it may be modified such that a message that theoriginator identification data is being received is displayed on the LCD28 to indirectly restrain the operation of sending a call or a responseto the incoming call, or a message that the operation of sending a callor a response to the incoming call is prohibited is displayed on the LCD28. At this time, a voice message may be generated from a voicesynthesizer circuit and output from the key telephone, instead offlickering the LED 26 or displaying a message on the LCD 28. Thisenables the user to recognize the message more clearly.

In addition, it is effective to continue the display of the originatoridentification data for a predetermined time even after the userresponds to the incoming call. The display may be continued until theentire speech is finished, or until a limited time such as about 1minute elapses from the start of speech. Moreover, it may be constructedsuch that the received originator identification data is registered in amemory, and read therefrom and displayed again when the user hasperformed a predetermined display operation after completion of thedisplay.

Second Embodiment

The second embodiment is characterized in that an electronic privatebranch exchange system is connected to an analog telephone networkhaving an originator notification function, and a notification controlfunction according to the invention is imparted to the electronicprivate branch exchange system. The notification control function causesa user to be notified of the incoming call after the notification of theoriginator identification data.

FIG. 8 is a block diagram, showing the electronic private branchexchange system according to the second embodiment. This systemcomprises an electronic private branch exchange 40 connected to theanalog telephone network NW via a plurality of subscriber lines, aplurality of extension telephones TEL1-TELk connected to the exchange 40via extension lines IL1-ILk, respectively, and a maintenance terminaldevice 47 provided as an auxiliary element of the exchange 40. Some ofthe extension telephones TEL1-TELk may have LCD displays and others maynot have such displays.

The electronic private branch exchange 40 comprises subscriber-lineinterface circuits TRK1-TRKj each connected to a correspondingsubscriber line, extension interface circuits LC1-LCk connected to theextension telephones TEL1-TELk via the extension lines IL1-ILk,respectively, an exchange circuit 41, an exchange control unit 42, a PBXcontroller 43, a memory circuit (MEM) 44 and an external interfacecircuits (IF) 45.

Each of the subscriber-line interface circuit TRK1-TRKj performssubscriber-line interface operations such as capture of a correspondingsubscriber line and detection of an incoming call transmittedtherethrough. Further, the subscriber-line interface circuits TRK1-TRKjhave a function for detecting the notification data supplied from theanalog telephone network NW, reproducing the originator identificationdata contained therein, and supplying the PBX controller 43 with anotice of the reproduced data.

Each of the extension interface circuits LC1-LCk performs extensioninterface operations such as detection of an outgoing call signaltransmitted through a corresponding extension line IL1-ILk, andtransmission of an incoming call signal through the same. Further, theextension interface circuits LC1-LCk have a function for ignoring, underthe control of the PBX controller 43, an outgoing call signal from anextension telephone to which an incoming call signal has occurred,during the time period from the detection of the first ringing signal ofthe incoming call signal to the detection of the originatoridentification data.

The exchange circuit 41 changes, under the control of the exchangecontrol unit 42, the connection between the extension interface circuitsLC1-LCk and between the extension interface circuits LC1-LCk and thesubscriber-line interface circuits TRK1-TRKj.

The memory circuit 44 is formed of a semiconductor memory such as a ROMor a RAM, or a hard disk, which stores a control program or variouscontrol data pieces for the PBX controller 43. The maintenance terminaldevice 47 consists, for example, of a personal computer, and is used tochange the control data pieces or set new control data pieces requiredfor control of the PBX controller 43.

The PBX controller 43 includes, for example, a microcomputer as a maincomponent, and has a function for controlling the time point of thenotification of the incoming call and that of the originatoridentification data. By virtue of this function, when the analogtelephone network NW has generated an incoming call signal to anextension telephone, an extension interface circuit corresponding to theextension telephone is supplied with an instruction to ignore a outgoingcall from the extension telephone until a corresponding subscriber-lineinterface circuit detects the originator identification data. At thesame time, the extension interface circuit is instructed to stop thetransmission of the incoming call signal to the extension telephoneduring the time period from the detection of the first ringing signal ofthe incoming call signal to the detection of the originatoridentification data.

As described above, in the electronic private branch exchange system ofthe second embodiment, when the analog telephone network NW hasgenerated an incoming call signal to an extension telephone, the PBXcontroller 43 supplies an extension interface circuit corresponding tothe extension telephone with instructions to prohibit the transmissionof the incoming call signal and the reception of an outgoing call signalduring the time period from the detection of the first ringing signal ofthe incoming call signal by a corresponding subscriber-line interfacecircuit to the detection of the originator identification data by thesubscriber-line interface circuit.

Accordingly, the extension telephone to which an incoming call hasoccurred is prevented from ringing until the originator identificationdata is detected, and therefore the user does not perform an operationfor responding to the incoming call. Further, if the user performs anoperation for sending a call before the originator identification datais detected, this operation is ignored by the extension interfacecircuit. As a result, the outgoing call is prevented from being sent tothe analog telephone network NW as a response to the incoming call. Thismeans that the originator identification data is reliably transmittedfrom the analog telephone network NW to a destination telephone.

The above-described second embodiment can be modified in the followingmanner. The extension telephones TEL1-TELk include a telephone with adisplay 48 such as TEL1 or TEL2, and a telephone with no display such asTELk. If an incoming call is transmitted to the telephone TELk with nodisplay, it is not necessary to prevent the notification of the incomingcall or the reception of an outgoing call from the telephone TELk untilthe originator identification data is detected.

This being so, when an incoming call signal to an extension telephonehas occurred, it is determined whether or not the telephone has afunction for displaying the originator identification data. If it isdetermined that the telephone does not have the display function, theincoming call signal is transmitted without stopping for thenotification of the incoming call signal and prohibiting the receptionof an outgoing call signal. Thus, the extension telephone TELk with nodisplay 48 is quickly supplied with a notice of the incoming callsignal, with unnecessary control interposed.

The second embodiment, too, can be modified in various manners like thefirst embodiment.

Third Embodiment

A third embodiment of the invention is characterized in that a telephonedevice with a display is connected to an analog telephone network havinga originator notification function, and is provided with a notificationcontrol function according to the invention, which causes a user to benotified of the incoming call after the notification of the originatoridentification data.

FIG. 9 is a block diagram, showing the circuit of the telephone devicewith a display according to the third embodiment. As is shown in FIG. 9,on the operation panel of the telephone device, there are a key group 54including dial keys and function keys, a display 56 and a speaker 58.The display 56 is, for example, a liquid crystal display (LCD). Thedisplay can display the time while an incoming call signal is awaited,and the originator identification data, the conversation time elapsed,etc. during conversation.

The internal circuit of the telephone device has a speech circuit 51connected to a subscriber line SL, a telephone controller 52, adetection circuit (DET) 53 and an LCD driver 55. The speech circuit 51is connected to a handset 57 and a speaker 58 for generating a ring tonotify of the incoming call. The detection circuit 53 has a function fordetecting a ringing signal and originator identification datatransmitted from the analog telephone network via the subscriber lineSL. The detection results are supplied to the telephone controller 52.

For example, the telephone controller 52 includes a microcomputer as amain component, and has a new function for controlling the timing of thenotification of each of the originator identification data and theincoming call, as well as general functions relating to the speechoperations. The new function is executed when the analog telephonenetwork has generated an incoming call signal, so as to prevent theoff-hook operation until the originator identification data is detected,and to cause the speaker 58 to ring after the detection of theoriginator identification data.

When in the telephone device constructed as above, the analog telephonenetwork has generated an incoming call signal, no ring is generated andthe off-hook operation is not allowed until at least the originatoridentification data is detected after detection of the first ringingsignal by the detection circuit 53. Thus, the originator identificationdata can reliably be received and detected.

The third embodiment, too, can be modified in various manners like thefirst embodiment.

Fourth Embodiment

A fourth embodiment of the invention is characterized in that a standardtelephone is connected, via an adaptor device, to a subscriber line ofan analog telephone network having an originator notification function,and is provided with a display function for displaying the originatoridentification data and a notification control function according to theinvention.

FIG. 10 is a block diagram,showing the circuit of the adaptor deviceaccording to the fourth embodiment. As is shown in FIG. 10, an adaptordevice 60 comprises a subscriber-line interface circuit 61 connected toa subscriber line SL, a telephone interface circuit 62 connected to astandard telephone 70, a switch (SW) 63 for connecting thesubscriber-line interface circuit 61 to the telephone interface circuit62, an adaptor controller 64 and a liquid crystal display (LCD) 65.

The subscriber-line interface circuit 61 performs varioussubscriber-line interface operations such as capture of the subscriberline and detection of an incoming call signal. Further, the circuit 61has a function for detecting notification data supplied from the analogtelephone network NW, reproducing the originator identification datacontained in the notification data, and supplying the adaptor controller64 with the originator identification data.

The telephone interface circuit 62 performs various telephone interfaceoperations such as detection of an outgoing call signal from thestandard telephone 70 and transmission of an incoming call signal to thestandard telephone 70. Further, the circuit 62 has a function, executedunder the control of the adaptor controller 64, for ignoring theoff-hook operation and stopping the supply of a signal for causing thespeaker to ring.

On the basis of the detection results regarding the ringing signal andthe originator identification data which are supplied from thesubscriber-line interface circuit 61, the adaptor controller 64 suppliesthe telephone interface circuit 62 with an instruction to ignore thereception of an off-hook signal from the standard telephone 70 and stopthe supply of a signal for causing the telephone 70 to ring, during thetime period from the detection of the first ringing signal to thedetection of the originator identification data. When the originatoridentification data has been detected, the controller 64 causes the LCD65 to display the data.

By virtue of the LCD 65 of the adaptor device 60, even the user who usesthe standard telephone 70 with no LCD can recognize the originatoridentification data. Further, since no incoming call signal is suppliedto the standard telephone 70 during the time period from the detectionof the first ringing signal to the reproduction of the originatoridentification data, the standard telephone 70 does not ring during thattime period. This prevents the user from performing the off-hookoperation for responding to the incoming call before the originatoridentification data is received. Moreover, since the off-hook operationof the standard telephone 70 is not allowed during the time period fromthe detection of the first ringing signal to the reproduction of theoriginator identification data, the originator identification data isreliably received even when the user has performed the off-hookoperation for sending a call without being aware of the incoming call.

The fourth embodiment, too, can be modified in various manners like thefirst embodiment.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A communication terminal connected via asubscriber line to a network having a function for transmitting aplurality of ringing signals to the communication terminal at regularintervals with an originator identification signal inserted in aninterval between a k-th (k: a predetermined integer) ringing signal anda (k+1)-th ringing signal, comprising:ringing signal detection means fordetecting the ringing signals transmitted from the network; originatordetection means for detecting the originator identification signaltransmitted from the network; and control means, connected to theringing signal detection means and the originator detection means, fornotifying a user of the communication terminal of originatoridentification data corresponding to the originator identificationsignal detected by the originator detection means, and starting tonotify the user of an incoming call in response to detection by theringing signal detection means of the (k+1)-th ringing signal, thecontrol means notifying the user of the communication terminal that theoriginator identification signal is being received during a time periodfrom the detection of a first ringing signal by the ringing signaldetection means to the detection of the originator identification signalby the originator detection means.
 2. The communication terminalaccording to claim 1, wherein the control means starts the notificationof the originator identification data and that of the incoming call atthe same time.
 3. The communication terminal according to claim 1,wherein the control means stores in a memory the originatoridentification data corresponding to the originator identificationsignal detected by the originator detection means, and reads the storeddata from the memory and sends the stored data in synchronism with thenotification of the incoming call performed in accordance with thedetection of the (k+1)-th ringing signal by the ringing signal detectionmeans.
 4. The communication terminal according to claim 1, wherein thecontrol means notifies the user of the communication terminal that anoperation for sending a call is prohibited, during a time period fromthe detection of the first ringing signal by the ringing signaldetection means to the detection of the originator identification signalby the originator detection means.
 5. The communication terminalaccording to claim 1, wherein the control means continues thenotification of the originator identification data for a predeterminedtime period even after an operation for responding to the incoming callis performed at the communication terminal.
 6. A key telephone systemconnected via at least one subscriber line to a network having afunction for transmitting a plurality of ringing signals to the keytelephone system at regular intervals, with an originator identificationsignal inserted in an interval between a k-th (k: a predeterminedinteger) ringing signal and a (k+1)-th ringing signal, comprising:a keytelephone control unit connected to the network via the at least onesubscriber line; and a plurality of key telephones connected to the keytelephone control unit via extension lines; wherein the key telephonecontrol unit includesringing signal detection means for detecting theringing signals transmitted from the network, originator detection meansfor detecting the originator identification signal transmitted from thenetwork, and control means, connected to the ringing signal detectionmeans and the originator detection means, for transmitting to at leastone of the key telephones via corresponding ones of the extension lines,originator identification data corresponding to the originatoridentification signal detected by the originator detection means, thecontrol means including means responsive to the ringing signals on andafter the (k+1)-th ringing signal for transmitting an incoming callsignal to the at least one of the key telephones via the correspondingones of the extension lines; and wherein at least one of the pluralityof key telephones includesmeans for receiving the originatoridentification data transmitted from the key telephone control unit viaa corresponding one of the extension lines, and notifying a user of thekey telephone of the received originator identification data, and meansresponsive to the incoming call signal transmitted from the keytelephone control unit via the corresponding extension line, fornotifying the user of the key telephone of an incoming call afternotification of the received originator identification data is started.7. The key telephone system according to claim 6, wherein the controlmeans transmits to the key telephones the originator identification datacorresponding to the originator identification signal detected by theoriginator detection means, and prohibits the transmission of theincoming call signal to the key telephones during a time period fromdetection of a first ringing signal by the ringing signal detectionmeans to the transmission of the originator identification data to thekey telephones.
 8. The key telephone system according to claim 6,wherein the key telephones start notification of the received originatoridentification data and notification of the incoming call at the sametime.
 9. The key telephone system according to claim 8, wherein each keytelephone stores in a memory the originator identification data from thekey telephone control unit, reads from the memory the originatoridentification data in response to the incoming call signal transmittedfrom the key telephone control unit, and notifies the user of the keytelephone of the incoming call and the originator identification data ina synchronized manner.
 10. The key telephone system according to claim6, wherein the control means of the key telephone control unit furtherincludes means for transmitting a detection result of the ringing signaldetection means to the key telephones via the extension lines when afirst ringing signal is detected by the ringing signal detection means,and each of the key telephones further includes means for notifying, ata time between a time of reception of the detection result from the keytelephone control unit and a time of reception of the originatoridentification data, the user of said each key telephone that theoriginator identification data is being received.
 11. The key telephonesystem according to claim 6, wherein the control means of the keytelephone control unit further includes means for transmitting adetection result of the ringing signal detection means to the keytelephones via the extension lines when a first ringing signal isdetected by the ringing signal detection means, and each of the keytelephones further includes means for notifying, at a time between atime of reception of the detection result from the key telephone controlunit and a time of reception of the originator identification data, theuser of said each key telephone that any transmission operation isprohibited.
 12. The key telephone system according to claim 6, whereineach of the key telephones starts notifying the user of the originatoridentification data when the incoming call is notified, and stopsnotifying the user of the originator identification data after apredetermined time period has elapsed after notification of the incomingcall.
 13. A key telephone system connected via at least one subscriberline to a network having a function for transmitting a plurality ofringing signals to the key telephone system at regular intervals, withan originator identification signal inserted in an interval between ak-th (k: a predetermined integer) ringing signal and a (k+1)-th ringingsignal, comprising:a key telephone control unit connected to the networkvia the at least one subscriber line; and a plurality of key telephonesconnected to the key telephone control unit via extension lines; whereinthe key telephone control unit includesringing signal detection meansfor detecting the ringing signals transmitted from the network,originator detection means for detecting the originator identificationsignal transmitted from the network, control means, connected to theringing signal detection means and the originator detection means, fortransmitting to at least one of the key telephones via correspondingones of the extension lines, originator identification datacorresponding to the originator identification signal detected by theoriginator detection means, the control means including means responsiveto the ringing signals on and after the (k+1)-th ringing signal fortransmitting an incoming call signal to the at least one of the keytelephones via the corresponding ones of the extension lines, pseudoincoming call signal means for generating a pseudo incoming call signalindependent of a detection result of the ringing signal detection means,and means for transmitting the pseudo incoming call signal generated bythe pseudo incoming call signal means to the key telephones via theextension lines; and wherein at least one of the plurality of keytelephones includesmeans for receiving the originator identificationdata transmitted from the key telephone control unit via a correspondingone of the extension lines, and notifying a user of the key telephone ofthe received originator identification data, means responsive to theincoming call signal transmitted from the key telephone control unit viathe corresponding extension line, for notifying the user of the keytelephone of an incoming call after notification of the originatoridentification data is started, and means responsive to the pseudoincoming call signal transmitted from the key telephone control unit viathe corresponding extension line, for notifying the user of the keytelephone of a pseudo incoming call corresponding to the pseudo incomingcall signal at a time between a start of notification of the receivedoriginator identification data and a start of notification of theincoming call.
 14. A private branch exchange system connected via atleast one subscriber line to a network having a function fortransmitting a plurality of ringing signals to the private branchexchange system at regular intervals, with an originator identificationsignal inserted in an interval between a k-th (k: a predeterminedinteger) ringing signal and a (k+1)-th ringing signal, comprising:aprivate branch exchange connected to the network via the at least onesubscriber line; and a plurality of extension telephones corrected tothe private branch exchange via extension lines; wherein the privatebranch exchange includesringing signal detection means for detecting theringing signals transmitted from the network, originator detection meansfor detecting the originator identification signal transmitted from thenetwork, and control means, connected to the ringing signal detectionmeans and the originator detection means, for transmitting to at leastone of the extension telephones via corresponding ones of the extensionlines, originator identification data corresponding to the originatoridentification signal detected by the originator detection means, thecontrol means including means responsive to ringing signals on and afterthe (k+1)-th ringing signal for transmitting an incoming call signal tothe at least one of the extension telephones via the corresponding onesof the extension line and wherein at least one of the extensiontelephones includesmeans for receiving the originator identificationdata transmitted from the private branch exchange via a correspondingone of the extension lines, and notifying a user of the extensiontelephone of the received originator identification data, and meansresponsive to the incoming call signal transmitted from the privatebranch exchange via the corresponding extension line, for notifying theuser of the extension telephone of an incoming call after notificationof the received originator identification data is started.
 15. Theprivate branch exchange system according to claim 14, wherein theextension telephones start notification of the received originatoridentification data and notification of the incoming call at the sametime.
 16. A private branch exchange system connected via at least onesubscriber line to a network having a function for transmitting aplurality of ringing signals to the private branch exchange system atregular intervals, with an originator identification signal inserted inan interval between a k-th (k: a predetermined integer) ringing signaland a (k+1)-th ringing signal, comprising:a private branch exchangeconnected to the network via the at least one subscriber line; and aplurality of extension telephones including at least one standardtelephone with no display function and at least one display-functionattached telephone with a display function, the at least one standardtelephone and the at least one display-function attached telephone beingconnected to the private branch exchange via respective extension lines;wherein the private branch exchange includes:ringing signal detectionmeans for detecting the ringing signals transmitted from the network,originator detection means for detecting the originator identificationsignal transmitted from the network, and exchange control meansconnected to the ringing signal detection means and the originatordetection means; the exchange control means having:destinationdetermination means for determining whether a destination extensiontelephone is the at least one standard telephone or the at least onedisplay-function attached telephone, first means operable when thedestination extension telephone has been determined to be the at leastone display-function attached telephone by the destination determinationmeans, the first means adapted to transmit, to the destination extensiontelephone, originator identification data corresponding to theoriginator identification signal detected by the originator detectionmeans, then to cause the destination extension telephone to display theoriginator identification data, and to transmit an incoming call signalto the destination extension telephone upon or after detection of the(k+1)-th ringing signal by the ringing signal detection means, therebyinforming a user of the destination extension telephone of an incomingcall, and second means operable when the destination extension telephonehas been determined to be the at least one standard extension telephoneby the destination determination means, the second means responding todetection of the k-th ringing signal by the ringing signal detectionmeans by transmitting an incoming call signal to the destinationextension telephone and thus informing the user of the destinationextension telephone of the incoming call.
 17. A key telephone systemconnected via at least one subscriber line to a network having afunction for transmitting a plurality of ringing signals to a privatebranch exchange at regular intervals, with an originator identificationsignal inserted in an interval between a k-th (k: a predeterminedinteger) ringing signal and a (k+1)-th ringing signal, comprising:a keytelephone control unit connected to the network via the at least onesubscriber line; and a plurality of extension telephones including atleast one standard telephone with no display function and at least keytelephone with a display function, the at least one standard telephoneand the at least key telephone being connected to the private branchexchange via respective extension lines; wherein the key telephonecontrol unit includes:ringing signal detection means for detecting theringing signals transmitted from the network, originator detection meansfor detecting the originator identification signal transmitted from thenetwork, and exchange control means connected to the ringing signaldetection means and the originator detection means; the exchange controlmeans having:destination determination means for determining whether adestination extension telephone is the at least one standard telephoneor the at least one key telephone, first means operable when thedestination extension telephone has been determined to be the at leastone key telephone by the destination determination means, the firstmeans adapted to transmit, to the destination extension telephone,originator identification data corresponding to the originatoridentification signal detected by the originator detection means, thento cause the destination extension telephone to display the originatoridentification data, and to transmit an incoming call signal to thedestination extension telephone upon or after detection of the (k+1)-thringing signal by the ringing signal detection means, thereby informinga user of the destination extension telephone of an incoming call, andsecond means operable when the destination extension telephone has beendetermined to be the at least one standard telephone by the destinationdetermination means, the second means responding to detection of thek-th ringing signal by the ringing signal detection means bytransmitting an incoming call signal to the destination extensiontelephone and thus informing the user of the destination extensiontelephone of the incoming call.